Poly(vinyl acetal) resin compositions, layers, and interlayers having enhanced properties

ABSTRACT

Resin compositions, layers, and interlayers comprising a poly(vinyl acetal) resin that includes residues of an aldehyde other than n-butyraldehyde are provided. Such compositions, layers, and interlayers can exhibit enhanced or optimized properties as compared to those formulated with comparable poly(vinyl n-butyral) resins.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.15/648,534 filed Jul. 13, 2017, which was a continuation of U.S. patentapplication Ser. No. 14/562,865, filed Dec. 8, 2014 now U.S. Pat. No.9,724,899, the disclosures of all which are hereby incorporated byreference herein.

BACKGROUND 1. Field of the Invention

This disclosure relates to polymer resins and, in particular, to polymerresins suitable for use in polymer interlayers, including those utilizedin multiple layer panels.

2. Description of Related Art

Poly(vinyl butyral) (PVB) is often used in the manufacture of polymersheets that can be used as interlayers in multiple layer panels,including, for example, light-transmitting laminates such as safetyglass or polymeric laminates. PVB is also used in photovoltaic solarpanels to encapsulate the panels which are used to generate and supplyelectricity for commercial and residential applications.

Safety glass generally refers to a transparent laminate that includes atleast one polymer sheet, or interlayer, disposed between two sheets ofglass. Safety glass is often used as a transparent barrier inarchitectural and automotive applications, and one of its primaryfunctions is to absorb energy resulting from impact or a blow withoutallowing penetration of the object through the glass and to keep theglass bonded even when the applied force is sufficient to break theglass. This prevents dispersion of sharp glass shards, which minimizesinjury and damage to people or objects within an enclosed area. Safetyglass may also provide other benefits, such as a reduction inultraviolet (UV) and/or infrared (IR) radiation, and it may also enhancethe aesthetic appearance of window openings through addition of color,texture, and the like. Additionally, safety glass with desirable soundinsulation properties has also been produced, which results in quieterinternal spaces.

Poly(vinyl acetal) resins typically include acetate pendant groups,hydroxyl pendant groups, and aldehyde pendant groups, such asn-butyraldehyde groups for a PVB resin, that are present along the vinylpolymer backbone. Properties of poly(vinyl acetal) resins aredetermined, in part, by the relative amount of hydroxyl, acetate, andaldehyde groups and/or by the type and amount of plasticizer added tothe resin. Therefore, selection of certain resin compositions andcombination of those resins with various types and amount ofplasticizers, can provide resin compositions, layers, and interlayershaving different properties.

However, such selections can have various drawbacks. For example, PVBresin compositions having high residual hydroxyl contents and lowplasticizer contents tend to have higher glass transition temperatures,which make such resins desirable in safety performance applications.However, these resins exhibit very poor vibration dampening and soundattenuation performance. Similarly, PVB resin compositions having lowerresidual hydroxyl contents and higher amounts of plasticizer may exhibitgood vibration and sound dampening properties, but typically havelimited, if any, impact resistance over a broad temperature range.

Thus, a need exists for polymer resins that exhibit multiple desirableproperties and that have mechanical, optical, and/or acoustic propertiesthat can be adjusted as needed so that the resin can be utilized in awide variety of applications. Additionally, a need exists for resincompositions, layers, and interlayers including such resins, which canbe employed in several end uses, including in safety glass and aspolymeric laminates.

SUMMARY

One embodiment of the present invention concerns an interlayercomprising a first resin layer comprising a first poly(vinyl acetal)resin and a first plasticizer; and a second resin layer adjacent to thefirst resin layer, wherein the second resin layer comprises a secondpoly(vinyl acetal) resin and a second plasticizer, wherein the secondplasticizer is present in the second resin layer in an amount of atleast 50 parts per hundred parts of resin (phr) and wherein thedifference between the amount of the first plasticizer in the firstresin layer and the amount of the second plasticizer in the second resinlayer is more than 10 phr, wherein at least one of the first and thesecond poly(vinyl acetal) resins comprises at least 5 weight percent ofresidues of an aldehyde other than n-butyraldehyde, based on the totalweight of aldehyde residues of the first or the second poly(vinylacetal) resin, and wherein the glass transition temperature of the firstresin layer is at least 3° C. higher than the glass transitiontemperature of the second resin layer, and wherein the absolute value ofthe difference between the refractive index of the first resin layer andthe refractive index of the second resin layer is not more than 0.010.

Another embodiment of the present invention concerns an interlayercomprising a first resin layer comprising a first poly(vinyl acetal)resin and a first plasticizer; and a second resin layer adjacent to thefirst resin layer, the second resin layer comprising a second poly(vinylacetal) resin and a second plasticizer, wherein the interlayer meets atleast one of the following criteria (i) through (iii): (i) the firstpoly(vinyl acetal) resin comprises at least 5 weight percent of residuesof i-butyraldehyde, based on the total weight of aldehyde residues ofthe first poly(vinyl acetal) resin, and the second poly(vinyl acetal)resin comprises at least 10 weight percent of residues of an aldehydehaving 6 or fewer carbon atoms, based on the total weight of aldehyderesidues of the second poly(vinyl acetal) resin, wherein the refractiveindex of the first resin layer is at least 0.002 lower than therefractive index of a comparable poly(vinyl n-butyral) resin layer, andwherein the residual hydroxyl content of the second poly(vinyl acetal)resin is not more than 12 weight percent and the difference between theresidual hydroxyl content of the first poly(vinyl acetal) resin and theresidual hydroxyl content of the second poly(vinyl acetal) resin is atleast 2 weight percent; (ii) the first poly(vinyl acetal) resincomprises at least 5 weight percent of residues of i-butyraldehyde,based on the total weight of aldehyde residues of the first poly(vinylacetal) resin, and the second poly(vinyl acetal) resin comprises atleast 10 weight percent of residues of an aldehyde having more than 6carbon atoms, based on the total weight of aldehyde residues of thesecond poly(vinyl acetal) resin, wherein the residual hydroxyl contentof the second poly(vinyl acetal) resin is at least 0.25 percent higherthan the residual hydroxyl content of the first poly(vinyl acetal)resin, and wherein the amount of the second plasticizer in the secondresin layer is at least 10 parts per hundred resin (phr) higher than theamount of the first plasticizer in the first resin layer; and (iii)neither of the first and the second poly(vinyl acetal) resins compriseresidues of i-butyraldehyde and the second resin layer has a glasstransition temperature that is at least 3° C. lower than the glasstransition temperature of a comparable poly(vinyl n-butyral) resinlayer.

Yet another embodiment of the present invention concerns a method ofmaking an interlayer, said method comprising the steps of forming afirst resin layer from a first poly(vinyl acetal) resin and a firstplasticizer; forming a second resin layer from a second poly(vinylacetal) resin and a second plasticizer; and producing said interlayerusing said first resin layer and said second resin layer, wherein saidfirst resin layer is adjacent to said second resin layer in saidinterlayer, wherein the glass transition temperature of said first resinlayer is at least 3° C. higher than the glass transition temperature ofsaid second resin layer, and wherein the difference between therefractive index of said first resin layer and the refractive index ofsaid second resin layer is not more than 0.010.

DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are described in detailbelow with reference to the attached drawing Figures, wherein:

FIG. 1 is a graph depicting the tan delta of several plasticizedpoly(vinyl acetal) resins described in Example 1, over a temperaturerange of 30° C. to 110° C.;

FIG. 2 is a graph depicting the tan delta of several plasticizedpoly(vinyl acetal) resins described in Example 3, over temperature rangeof −30 to 60° C.;

FIG. 3 is a graph depicting the refractive index of several poly(vinylacetal) resins described in Example 4 as a function of plasticizercontent;

FIG. 4 is a graph depicting the cloud point of two poly(vinyl acetal)resins described in Example 8 as a function of residual hydroxylcontent;

FIG. 5 is a graph depicting the tan delta of several plasticized resincompositions described in Example 9 over a temperature range of −20° C.to 30° C.;

FIG. 6a is a graph depicting the glass transition temperature of severalplasticized resins described in Example 10 as a function of plasticizerloading; and

FIG. 6b is a graph depicting the tan delta of the resin compositionsdescribed in Example 10 and shown in FIG. 6a as a function of glasstransition temperature.

DETAILED DESCRIPTION

The present invention relates to polymer resin compositions, layers, andinterlayers that include at least one poly(vinyl acetal) resin thatexhibits different properties than a conventional poly(vinyl n-butyral)(PVB) resin, but that can be used in many of the same applications asPVB, including, for example, safety glass applications. Compositions,layers, and interlayers according to various embodiments of the presentinvention may have different glass transition temperatures, differentrefractive indices, and/or different viscosities than comparablepoly(vinyl acetal) resins that only include residues of n-butyraldehyde.As a result, the resins, compositions, layers, and interlayers describedherein may also exhibit enhanced optical, mechanical, and/or acousticperformance. Methods for producing compositions, layers, and interlayershaving optimized properties according to various embodiments of thepresent invention are also described herein.

As used herein, the terms “polymer resin composition” and “resincomposition” refer to compositions that include one or more polymerresins. Polymer compositions may optionally include other components,such as plasticizers and/or other additives. As used herein, the terms“polymer resin layer” and “resin layer” refer to one or more polymerresins, optionally combined with one or more plasticizers, that havebeen formed into a polymeric sheet. Again, resin layers may include oneor more additional additives. As used herein, the term “interlayer”refers to a single or multiple layer polymer sheet suitable for use withat least one rigid substrate to form a multiple layer panel. The terms“single-sheet” and “monolithic” interlayer refer to interlayers formedof one single resin sheet, while the terms “multiple layer” and“multilayer” interlayer refer to interlayers having two or more resinsheets that are coextruded, laminated, or otherwise coupled to oneanother.

Resin compositions, layers, and interlayers according to variousembodiments of the present invention can include at least one poly(vinylacetal) resin. Poly(vinyl acetal) resins can be formed by aqueous orsolvent-based acetalization of poly(vinyl alcohol) with one or morealdehydes in the presence of an acid catalyst. The resulting resin canthen be separated, stabilized, and dried according to known methods suchas, for example, those described in U.S. Pat. Nos. 2,282,057 and2,282,026, as well as “Vinyl Acetal Polymers,” in the Encyclopedia ofPolymer Science & Technology, 3^(rd) ed., Volume 8, pages 381-399, by B.E. Wade (2003). The total amount of residual aldehyde groups, orresidues, present in the resulting poly(vinyl acetal) resin can be atleast about 50, at least about 60, at least about 70, at least about 75,at least about 80, at least about 85, at least about 90, at least about92 weight percent, as measured by ASTM D-1396. The total amount ofaldehyde residues in a poly(vinyl acetal) resin can be collectivelyreferred to as the acetal component, with the balance of the poly(vinylacetal) resin comprising residual hydroxyl or acetate groups, which willbe discussed in further detail below.

When the poly(vinyl acetal) resin is a poly(vinyl n-butyral) (PVB)resin, greater than 90, at least about 95, at least about 97, or atleast about 99 percent, by weight, of the acetal component, or totalaldehyde residues, can comprise residues of n-butyraldehyde.Additionally, a poly(vinyl n-butyral) resin may comprise less than 10,not more than about 5, not more than about 2, not more than about 1, ornot more than about 0.5 weight percent of residues of an aldehyde otherthan n-butyraldehyde, based on the total weight of aldehyde residues ofthat resin.

Compositions, layers, and interlayers according to embodiments of thepresent invention can include at least one poly(vinyl acetal) resin thatcomprises at least about 10 weight percent of residues of an aldehydeother than n-butyraldehyde. In some embodiments, the poly(vinyl acetal)resin may include at least about 15, at least about 20, at least about30, at least about 40, at least about 50, at least about 60, at leastabout 70, at least about 80, at least about 90, at least about 95, or atleast about 99 weight percent of residues of an aldehyde other thann-butyraldehyde, based on the total weight of aldehyde residues of thepoly(vinyl acetal) resin. This resin may also include not more thanabout 10, not more than about 5, not more than about 2, or not more thanabout 1 weight percent of residues of n-butyraldehyde, based on thetotal weight of aldehyde residues of the poly(vinyl acetal) resin.

When the poly(vinyl acetal) resin includes residues of one or morealdehydes other than n-butyraldehyde, any suitable aldehyde can be used.In some embodiments, the aldehyde other than n-butyraldehyde cancomprise, for example, an aldehyde having between 3 and 12 carbon atomsper molecule (i.e., a C₃ to C₁₂ aldehyde), an aldehyde having between 4and 10 carbon atoms per molecule (i.e., a C₄ to C₁₀ aldehyde), or analdehyde having between 4 and 8 carbon atoms per molecule (i.e., a C₄ toC₈ aldehyde), except n-butyraldehyde. In some embodiments, the aldehydecan include 8 or fewer carbon atoms per molecule, 6 or fewer carbonatoms per molecule, or 4 or fewer carbon atoms per molecule. In otherembodiments, the aldehyde can have more than 4 carbon atoms permolecule, more than 5 carbon atoms per molecular, or more than 6 carbonatoms per molecule.

The aldehyde other than n-butyraldehyde may be an aliphatic aldehyde andcan be either a branched or a straight chain molecule. Examples ofsuitable aldehydes other than n-butyraldehyde can include, but are notlimited to, i-butyraldehyde, 2-methylvaleraldehyde, n-hexyl aldehyde,2-ethylhexyl aldehyde, n-octyl aldehyde, and combinations thereof. Insome embodiments, the aldehyde other than n-butyraldehyde can beselected from the group consisting of i-butyraldehyde,2-methylbutyraldehyde, 2-ethylhexyl aldehyde, and combinations thereof,while, in some embodiments, the aldehyde other than n-butyraldehyde canbe selected from the group consisting of i-butyraldehyde, 2-ethylhexylaldehyde, and combinations thereof.

According to various embodiments, the resin composition, layer, orinterlayer may also include a poly(vinyl acetal) resin comprisingresidues of n-butyraldehyde. In some embodiments, these residues ofn-butyraldehyde may be present in the same resin having residues of analdehyde other than n-butyraldehyde, thereby forming a single “hybrid”resin with multiple aldehyde residues. In other embodiments, then-butyraldehyde residues may be present on a second poly(vinyl acetal)resin physically blended with the first poly(vinyl acetal) resin thatincludes residues of an aldehyde other than n-butyraldehyde, and theblend can be present in the composition, layer, or interlayer.Typically, for every blend of resins, an equivalent single hybridpoly(vinyl acetal) resin also exists that may be substituted for theblend with similar results.

When the composition, layer, or interlayer includes a single hybridresin having residues of different aldehydes, the residues of thealdehyde other than n-butyraldehyde and the residues of n-butyraldehydemay each be present in the resin in an amount of at least about 1, atleast about 2, at least about 5, at least about 10, at least about 15,at least about 20, at least about 25, at least about 30, at least about35, at least about 40, or at least about 45 percent, based on the totalweight of the aldehyde residues of the single resin. The combined amountof these two residues can comprise at least about 40, at least about 50,at least about 60, at least about 70, at least about 80, or at leastabout 90 percent of the total weight of the aldehyde residues of theresin. In some embodiments, the ratio, by weight, of residues of thealdehyde other than n-butyraldehyde to the n-butyraldehyde residues canbe at least about 1:99, at least about 5:95, at least about 10:90, atleast about 15:85, at least about 25:75, at least about 30:70, at leastabout 40:60 and/or not more than about 99:1, not more than about 95:5,not more than about 90:10, not more than about 85:15, not more thanabout 75:25, not more than about 70:30, not more than about 60:40, or inthe range of from about 1:99 to about 99:1, about 5:95 to about 95:5,about 10:90 to about 90:10, about 15:85 to about 85:15, about 25:75 toabout 75:25, about 30:70 to about 70:30, or about 40:60 to about 60:40,or the residues of the aldehyde other than n-butyraldehyde can bepresent in the poly(vinyl acetal) resin in an amount of at least about1, at least about 5, at least about 10, at least about 15, at leastabout 25, at least about 30, or at least about 40 weight percent, basedon the combined weight of the residues of the aldehyde other thann-butyraldehyde and the residues of n-butyraldehyde.

Similarly, when the composition, layer, or interlayer comprises aphysical blend of a first poly(vinyl acetal) resin comprising residuesof an aldehyde other than n-butyraldehyde and a second poly(vinylacetal) resin comprising residues of n-butyraldehyde, each of thepoly(vinyl acetal) resins may be present in the composition, layer, orinterlayer in an amount of at least about 1, at least about 2, at leastabout 5, at least about 10, at least about 15, at least about 20, atleast about 30, at least about 40, or at least about 45 weight percent,based on the total weight of the resins in the composition. Together,the combined amount of the first and second poly(vinyl acetal) resinscan make up at least about 40, at least about 50, at least about 60, atleast about 70, at least about 80, or at least about 90 percent of thetotal weight of the resins in the composition, layer, or interlayer.

When the resin composition, layer, or interlayer includes a blend of afirst and a second poly(vinyl acetal) resin, the ratio, by weight, ofthe first poly(vinyl acetal) resin to the second poly(vinyl acetal)resin can be in the range of from about 1:99 to 99:1, about 5:95 to95:5, about 10:90 to 90:10, about 15:85 to 85:15, about 25:75 to 75:25,about 30:70 to 70:30, or about 40:60 to 60:40. In some embodiments, thefirst poly(vinyl acetal) resin, which can include residues of analdehyde other than n-butyraldehyde, can be present in the composition,layer, or interlayer in an amount of at least about 1, at least about 5,at least about 10, at least about 15, at least about 25, at least about30, or at least about 40 weight percent, based on the combined weight ofthe first and second resins.

In addition to residues of one or more aldehydes, the poly(vinyl acetal)resins described herein may also include residual hydroxyl and/orresidual acetate groups. As used herein, the terms “residual hydroxylcontent” and “residual acetate content” refer to the amount of polyvinylhydroxyl and polyvinyl acetate groups, respectively, that remain on aresin after processing is complete. For example, poly(vinyl n-butyral)can be produced by hydrolyzing poly(vinyl acetate) to poly(vinylalcohol), and then acetalizing the poly(vinyl alcohol) withn-butyraldehyde to form poly(vinyl n-butyral). In the process ofhydrolyzing the poly(vinyl acetate), not all of the acetate groups areconverted to hydroxyl groups, and residual acetate groups remain on theresin. Similarly, in the process of acetalizing the poly(vinyl alcohol),not all of the hydroxyl groups are converted to acetal groups, whichalso leaves residual hydroxyl groups on the resin. As a result, mostpoly(vinyl acetal) resins include both residual hydroxyl groups (asvinyl hydroxyl, PVOH, groups) and residual acetate groups (as vinylacetate, PVAc, groups) as part of the polymer chain. The residualhydroxyl content and residual acetate content are expressed in weightpercent, based on the weight of the polymer resin, and are measuredaccording to ASTM D-1396.

In various embodiments, one or more of the poly(vinyl acetal) resinspresent in a composition, layer, or interlayer may have a residualhydroxyl content of at least about 14, at least about 14.5, at leastabout 15, at least about 15.5, at least about 16, at least about 16.5,at least about 17, at least about 17.5, at least about 18, at leastabout 18.5, at least about 19, at least about 19.5 and/or not more thanabout 45, not more than about 40, not more than about 35, not more thanabout 33, not more than about 30, not more than about 27, not more thanabout 25, not more than about 23, not more than about 22, not more thanabout 21.5, not more than about 21, not more than about 20.5, not morethan about 20, not more than about 19.5, not more than about 19, notmore than about 18.7 weight percent, measured as described previously.The residual hydroxyl content can be in the range of from about 14 toabout 45, about 16 to about 30, about 18 to about 25, about 18.5 toabout 20, or about 19.5 to about 21 weight percent.

In some embodiments, at least one poly(vinyl acetal) resin can have aresidual hydroxyl content of at least about 8, at least about 8.5, atleast about 9, at least about 9.5 weight percent and/or not more thanabout 13, not more than about 12.5, not more than about 12, not morethan about 11.5, not more than about 11, not more than about 10.5, notmore than about 10, not more than about 9.5, or not more than about 9weight percent, or in the range of from about 8 to about 13, about 9 toabout 12, or about 9.5 to about 11.5 weight percent.

When two or more poly(vinyl acetal) resins are present in a resincomposition, layer, or interlayer as described herein, one or more ofthe resins can have a residual hydroxyl content different from theresidual hydroxyl content of one or more of the other resins. Forexample, when a resin composition, layer, or interlayer includes a firstpoly(vinyl acetal) resin and a second poly(vinyl acetal) resin, at leastone of the resins can have a residual hydroxyl content that is at least2 weight percent different than the other. One or both resins caninclude residues of an aldehyde other than n-butyraldehyde as describedpreviously. As used herein, the terms “weight percent different” and“the difference . . . is at least . . . weight percent” refer to adifference between two given weight percentages, calculated bysubtracting one number from the other number. For example, a poly(vinylacetal) resin having a residual hydroxyl content of 12 weight percentand a poly(vinyl acetal) resin having a residual hydroxyl content of 14weight percent have a weight percent difference of 2. As used herein,the term “different” encompasses values that are both higher and lowerthan another value.

According to some embodiments, the residual hydroxyl content of onepoly(vinyl acetal) resin can be at least about 3, at least about 4, atleast about 6, or at least about 8 weight percent higher or lower thanthe residual hydroxyl content of another. In some embodiments, thedifference between the residual hydroxyl content of one of thepoly(vinyl acetal) resins and the residual hydroxyl content of anotherof the poly(vinyl acetal) resins in the compositions, layers, andinterlayers described herein can be at least about 10, at least about12, at least about 15, at least about 20, or at least about 30 weightpercent.

When a resin composition, layer, or interlayer comprises two poly(vinylacetal) resins having different residual acetate contents, thedifference in residual acetate contents between two of the resins can beat least about at least about 2, at least about 4, at least about 6, atleast about 8, at least about 10, at least about 12 and/or not more thanabout 30, not more than about 20, not more than about 15, or not morethan about 10 weight percent, or the difference can be in the range offrom about 2 to about 30, about 4 to about 20, about 6 to about 15, orabout 8 to about 10 weight percent. For example, in some embodiments, atleast one of the poly(vinyl acetal) resins described herein can have aresidual acetate content of not more than about 4, not more than about3, not more than about 2, or not more than about 1 weight percent,measured as described previously. In some embodiments, at least anotherof the poly(vinyl acetal) resins may have a residual acetate content ofat least about 8, at least about 10, at least about 12, at least about14, at least about 16, at least about 18, or at least about 20 weightpercent.

In some embodiments, when the resin composition, layer, or interlayerincludes a physical blend of resins, the first and second poly(vinylacetal) resins may be blended such that one of the first and secondpoly(vinyl acetal) resins is dispersed within the other of the first andsecond poly(vinyl acetal) resins, which can form domains of one of thefirst and second poly(vinyl acetal) resins within the other of the firstand second poly(vinyl acetal) resins. Such a blended resin may be usedas a single layer interlayer or it may be combined with one or moreadjacent layers to form a multilayer interlayer. In other embodiments,the first and second poly(vinyl acetal) resins can be present inadjacent layers of a multilayer interlayer, such that one of the layersof the interlayer includes the first poly(vinyl acetal) resin andanother layer of the interlayer includes the second poly(vinyl acetal)resin. Additional layers can also be present adjacent to at least one ofthe layers.

The resin compositions, layers, and interlayers according to variousembodiments of the present invention can further include at least oneplasticizer. Depending on the specific composition of the resin orresins in a composition, layer, or interlayer, the plasticizer may bepresent in an amount of at least about 5, at least about 10, at leastabout 15, at least about 20, at least about 25, at least about 30, atleast about 35, at least about 40, at least about 42, at least about 45,at least about 50, at least about 55, at least about 60, at least about65, at least about 70 parts per hundred parts of resin (phr) and/or notmore than about 120, not more than about 110, not more than about 105,not more than about 100, not more than about 95, not more than about 90,not more than about 85, not more than about 75, not more than about 70,not more than about 65, not more than about 60, not more than about 55,not more than about 50, not more than about 45, or not more than about40 phr, or in the range of from about 5 to about 120, about 10 to about110, about 20 to about 90, or about 25 to about 75 phr.

As used herein, the term “parts per hundred parts of resin” or “phr”refers to the amount of plasticizer present as compared to one hundredparts of resin, on a weight basis. For example, if 30 grams ofplasticizer were added to 100 grams of a resin, the plasticizer would bepresent in an amount of 30 phr. If the resin composition, layer, orinterlayer includes two or more resins, the weight of plasticizer iscompared to the combined amount of the resins present to determine theparts per hundred resin. Further, when the plasticizer content of alayer or interlayer is provided herein, it is provided with reference tothe amount of plasticizer in the mix or melt that was used to producethe layer or interlayer.

In some embodiments, the plasticizer may be present in an amount of atleast about 42, at least about 45, at least about 50, at least about 55,at least about 60, at least about 65, or at least about 70 phr, while,in some embodiments, the plasticizer may be present in an amount of notmore than about 50, not more than about 45, not more than about 42, notmore than about 40, not more than about 38, not more than about 35, notmore than about 30, not more than about 30, not more than about 25, notmore than about 20, not more than about 17, not more than about 15, notmore than about 12, or not more than about 10 phr.

Examples of suitable plasticizers can include, but are not limited to,triethylene glycol di-(2-ethylhexanoate) (“3GEH”), triethylene glycoldi-(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethyleneglycol diheptanoate, tetraethylene glycol di-(2-ethylhexanoate)(“4GEH”), polyethylene glycol bis(2-ethylhexanoate), dipropylene glycoldibenzoate, dihexyl adipate, dioctyl adipate, hexyl cyclohexyladipate,diisononyl adipate, heptylnonyl adipate, di(butoxyethyl) adipate, andbis(2-(2-butoxyethoxy)ethyl) adipate, dibutyl sebacate, dioctylsebacate, and mixtures thereof. The plasticizer may be selected from thegroup consisting of triethylene glycol di-(2-ethyl hexanoate),tetraethylene glycol di-(2-ethyl hexanoate), and combinations thereof.In some embodiments, at least two plasticizers may be present in thecompositions, layers, and interlayers described herein, with one of theplasticizers enhancing the compatibility of one or more otherplasticizers in the composition. The refractive index, measuredaccording to ASTM D542 at a wavelength of 589 nm and 25° C., of one orall plasticizers in the composition can be at least about 1.440, atleast about 1.442, at least about 1.445 and/or not more than about1.500, not more than about 1.475, not more than about 1.460, not morethan about 1.455, or not more than about 1.450, or in the range of fromabout 1.440 to about 1.500, about 1.442 to about 1.475, about 1.445 toabout 1.460.

One or more resin compositions, layers, and interlayers described hereinmay include various other additives to impart particular properties orfeatures to the interlayer. Such additives can include, but are notlimited to, dyes, pigments, stabilizers such as ultraviolet stabilizers,antioxidants, anti-blocking agents, flame retardants, IR absorbers orblockers such as indium tin oxide, antimony tin oxide, lanthanumhexaboride (LaB₆) and cesium tungsten oxide, processing aides, flowenhancing additives, lubricants, impact modifiers, nucleating agents,thermal stabilizers, UV absorbers, dispersants, surfactants, chelatingagents, coupling agents, adhesives, primers, reinforcement additives,and fillers.

Additionally, various adhesion control agents (“ACAs”) can be used inthe interlayers of the present disclosure to control the adhesion of thesheet to glass. In various embodiments, the amount of ACAs present in aresin composition, layer, or interlayer can be at least about 0.003, atleast about 0.01, at least about 0.025 and/or not more than about 0.15,not more than about 0.10, or not more than about 0.04 phr, or in therange of from about 0.003 to about 0.15, about 0.01 to about 0.10, orabout 0.025 to about 0.04 phr. Suitable ACAs can include, but are notlimited to, residual sodium acetate, potassium acetate, magnesiumbis(2-ethyl butyrate), magnesium bis(2-ethylhexanoate), and combinationsthereof, as well as the ACAs disclosed in U.S. Pat. No. 5,728,472.

When two or more poly(vinyl acetal) resins are utilized in a resincomposition, layer, or interlayer, and at least one of the resins has aresidual hydroxyl and/or acetate contents different from one or moreother resins, the differences may be selected to control or providecertain performance properties, such as strength, impact resistance,penetration resistance, processability, or acoustic performance to thefinal composition, layer, or interlayer. For example, poly(vinyl acetal)resins having a higher residual hydroxyl content, usually greater thanabout 14 weight percent, can facilitate increased impact resistance,penetration resistance, and strength to a resin composition or layer,while lower hydroxyl content resins, usually having a residual hydroxylcontent of less than 13 weight percent, can improve the acousticperformance of the interlayer or blend.

Poly(vinyl acetal) resins having higher or lower residual hydroxylcontents and/or residual acetate contents, when combined with at leastone plasticizer, ultimately include different amounts of plasticizer. Asa result, different layers within a multilayered interlayer, forexample, may have different properties. Although not wishing to be boundby theory, it is understood that the compatibility of a givenplasticizer with a poly(vinyl acetal) resin can depend, at least inpart, on the composition of the polymer, and, in particular, on itsresidual hydroxyl content. Overall, poly(vinyl acetal) resins withhigher residual hydroxyl contents tend to exhibit a lower compatibility(or capacity) for a given plasticizer as compared to similar resinshaving a lower residual hydroxyl content. As a result, poly(vinylacetal) resins with higher residual hydroxyl contents tend to be lessplasticized and exhibit higher stiffness than similar resins havinglower residual hydroxyl contents. Conversely, poly(vinyl acetal) resinshaving lower residual hydroxyl contents may tend to, when plasticizedwith a given plasticizer, incorporate higher amounts of plasticizer,which may result in a softer resin layer that exhibits a lower glasstransition temperature than a similar resin having a higher residualhydroxyl content. Depending on the specific resin and plasticizer,however, these trends could be reversed.

When two poly(vinyl acetal) resins having different levels of residualhydroxyl content are blended with a plasticizer, the plasticizer maypartition between the resin layers or domains, such that moreplasticizer can be present in the layer or domain having the lowerresidual hydroxyl content and less plasticizer may be present in thelayer or domain having the higher residual hydroxyl content. Ultimately,a state of equilibrium is achieved between the two resins. Thecorrelation between the residual hydroxyl content of a poly(vinylacetal) resin and plasticizer compatibility/capacity can facilitateaddition of a proper amount of plasticizer to the polymer resin. Such acorrelation also helps to stably maintain the difference in plasticizercontent between two or more resins when the plasticizer would otherwisemigrate between the resins.

In some embodiments, when the resin layer or interlayer includes atleast a first resin layer comprising a first poly(vinyl acetal) resinand a first plasticizer, and a second resin layer, adjacent to the firstresin layer, comprising a second poly(vinyl acetal) resin and a secondplasticizer, the resin layers may have different plasticizer contents.For example, the difference in plasticizer content between the resinlayers can be at least about 2, at least about 5, at least about 8, atleast about 10, at least about 12, or at least about 15 phr. In mostembodiments, the resin layer that includes the resin having a lowerhydroxyl content can have the higher plasticizer content. In order tocontrol or retain other properties of the resin layer or interlayer, thedifference in plasticizer content between the first and second resinlayers may be not more than about 30, not more than about 25, not morethan about 20, or not more than about 17 phr.

In some embodiments, the first and second resin layers can exhibitdifferent glass transition temperatures. Glass transition temperature,or T_(g), is the temperature that marks the transition from the glassstate of the polymer to the rubbery state. The glass transitiontemperatures of the resins and layers described herein were determinedby dynamic mechanical thermal analysis (DTMA). The DTMA measures thestorage (elastic) modulus (G′) in Pascals, loss (viscous) modulus (G″)in Pascals, and the tan delta (G″/G′) of the specimen as a function oftemperature at a given frequency and temperature sweep rate. The glasstransition temperature was then determined by the position of the tandelta peak on the temperature scale. Glass transition temperaturesprovided herein were determined at a frequency of 1 Hz and a sweep rateof 3° C./min.

The difference in the glass transition temperature of the first resinlayer and the glass transition temperature of the second resin layer canbe at least about 3, at least about 5, at least about 8, at least about10, at least about 12, at least about 15, at least about 18, at leastabout 20, at least about 22, or at least about 25° C. One of the firstand second resin layers can have a glass transition temperature of atleast about 25, at least about 27, at least about 30, at least about 33,at least about 35, at least about 37° C. and/or not more than about 70,not more than about 65, not more than about 60, not more than about 55,not more than about 50° C., or in the range of from about 25 to about70, about 27 to about 60, about 35 to about 50. The other of the firstand second poly(vinyl acetal) resins can have a glass transitiontemperature of less than 25, not more than about 20, not more than about15, not more than about 10, not more than about 5, not more than about2, not more than about 1, not more than about 0, not more than about −1,not more than about −2° C.

According to various embodiments of the present invention, resincompositions, layers, and interlayers as described herein that includeat least one poly(vinyl acetal) resin having residues of an aldehydeother than n-butyraldehyde may exhibit different properties, such as,for example, glass transition temperature, refractive index, and tandelta, as compared to similar resin compositions, layers, andinterlayers formed using conventional poly(vinyl n-butyral) resins.

For example, in some embodiments, poly(vinyl acetal) resins includingresidues of aldehydes other than n-butyraldehyde may have a differentmolecular weight than a comparable poly(vinyl n-butyral) resin. As usedherein, the term “comparable poly(vinyl n-butyral) resin” refers to apoly(vinyl acetal) resin having the same residual acetal, residualhydroxyl, and acetate content as a given poly(vinyl acetal) resin, butthat includes an acetal component including only residues ofn-butyraldehyde. In various embodiments, the poly(vinyl acetal) resinthat includes residues of an aldehyde other than n-butyraldehyde canhave a molecular weight that is at least about 5, at least about 10, atleast about 15, or at least about 20 percent higher or lower than themolecular weight of a comparable poly(vinyl n-butyral) resin.

In some embodiments, the molecular weight of the poly(vinyl acetal)resin including residues of an aldehyde other than n-butyraldehyde canbe lower than a comparable poly(vinyl n-butyral) resin. The molecularweight of poly(vinyl acetal) resins comprising residues of an aldehydeother than n-butyraldehyde may be at least about 10,000, at least about15,000, at least about 20,000, at least about 25,000 and/or not morethan about 250,000, not more than about 200,000, not more than about150,000, not more than about 100,000, or not more than about, or lessthan about, 50,000 Daltons, or in the range of from about 10,000 toabout 250,000, about 15,000 to about 200,000, about 20,000 to about150,000, or about 25,000 to about 50,000 Daltons. In contrast, apoly(vinyl n-butyral) (PVB) resin may have a molecular weight of atleast about 50,000, at least about 70,000, at least about 80,000, atleast about 90,000, at least about 100,000 Daltons and/or not more thanabout 600,000, not more than about 550,000, not more than about 500,000,not more than about 450,000, not more than about 425,000, or not morethan about 325,000 Daltons, measured by size exclusion chromatographyusing low angle laser light scattering (SEC/LALLS) method of Cotts andOuano. As used herein, the term “molecular weight” refers to the weightaverage molecular weight (M_(w)). The molecular weight of the PVB resincan be in the range of from about 50,000 to about 600,000, about 70,000to about 450,000, about 80,000 to about 425,000, or about 90,000 toabout 325,000 Daltons.

In some embodiments, poly(vinyl acetal) resin having residues of analdehyde other than n-butyraldehyde can have higher compatibility with aplasticizer than a comparable poly(vinyl n-butyral) resin. Highercompatibility of a poly(vinyl acetal) resin in a given plasticizer canbe measured as the cloud point of the resin in that plasticizer. As usedherein, the term “cloud point” refers to the temperature at which adissolved solid is no longer completely soluble in a liquid. Cloud pointis measured by mixing 0.05 grams of resin with 1.95 grams of aplasticizer at room temperature and then heating the mixture in asilicone oil bath under continuous stirring conditions until the resinis completely dissolved and the solution is clear. The heating is thenstopped and the temperature continuously monitored. The temperature atwhich the solution begins to cloud, which indicates precipitation ofsolid resin from the solution, is the cloud point temperature.

In some embodiments, poly(vinyl acetal) resins that include residues ofan aldehyde other than n-butyraldehyde can have a lower cloud point thana comparable poly(vinyl n-butyral) resin in one or more plasticizers.For these plasticizers, this indicates higher compatibility with theplasticizer than a comparable poly(vinyl n-butyral) resin. In someembodiments, the poly(vinyl acetal) resin comprising residues of analdehyde other than n-butyraldehyde can have a cloud point temperaturethat is at least about 1, at least about 2, at least about 5, or atleast about 10° C. lower than the cloud point temperature of acomparable poly(vinyl n-butyral) resin in a given plasticizer. Theplasticizer can be one or more of those listed above.

Additionally, poly(vinyl acetal) resins comprising residues of analdehyde other than n-butyraldehyde may have a lower viscosity than acomparable poly(vinyl n-butyral) resin. For example, in someembodiments, the viscosity of a poly(vinyl acetal) resin comprisingresidues of an aldehyde other than n-butyraldehyde can be at least about5, at least about 10, at least about 15, or at least about 20 percentlower than the viscosity of a comparable poly(vinyl n-butyral) resin. Asused herein, solution viscosity was measured using a Cannon Fenskecapillary viscometer size 400, commercially available from CannonInstrument Company, State College, Pa., at 20° C. in a 7.5 percentmethanol solution. Once the solution has been prepared, the solution isallowed to equilibrate in a 20° C.±0.1° C. water bath for at least 30minutes. The viscometer is placed in the water bath and 10 mL of thesolution is transferred to the viscometer using a fast flow pipette bypressing the fluid with a pressure bulb to beyond the upper mark of theviscometer, and recording the time taken by the liquid level to passbetween the upper and lower marks. The viscosity of a poly(vinyl acetal)resin comprising residues of an aldehyde other than n-butyraldehyde canbe at least about 5, at least about 10, at least about 15, at leastabout 20, or at least about 30 centipoise (cps) lower than the viscosityof a comparable poly(vinyl n-butyral) resin.

Additionally, a poly(vinyl acetal) resin comprising residues of analdehyde other than n-butyraldehyde may also have a glass transitiontemperature that is different than the glass transition temperature of acomparable poly(vinyl butyral) resin. For example, the glass transitiontemperature of the poly(vinyl acetal) resin including residues of analdehyde other than n-butyraldehyde can be at least about 5, at leastabout 10, at least about 15, at least about 20, or at least about 25percent higher or lower than the glass transition temperature of acomparable poly(vinyl n-butyral) resin. The glass transition temperatureof the poly(vinyl acetal) resin comprising residues of an aldehyde otherthan n-butyraldehyde can be at least about 2, at least about 3, at leastabout 3.5, at least about 4, at least about 4.5, at least about 5, atleast about 6, at least about 10, or at least about 12° C. higher orlower than the glass transition temperature of a comparable poly(vinyln-butyral) resin.

In some embodiments, the poly(vinyl acetal) resin including residues ofan aldehyde other than n-butyraldehyde may have a glass transitiontemperature of not more than about 83, not more than about 82, not morethan about 80, not more than about 75, not more than about 70, not morethan about 65, not more than about 60, or not more than about 55° C.,while in other embodiments, the glass transition temperature of thepoly(vinyl acetal) resin comprising residues of an aldehyde other thann-butyraldehyde can be at least about 80, at least about 82, at leastabout 83, at least about 84, at least about 85, or at least about 86°C., measured as described previously. When two or more poly(vinylacetal) resins are present in a composition, layer, or interlayer, thedifference in glass transition temperature between one of the resins andat least one or more other resins can be at least about 2, at leastabout 5, at least about 10, or at least about 15° C.

Further, poly(vinyl acetal) resins comprising residues of an aldehydeother than n-butyraldehyde may also have a refractive index differentthan a comparable poly(vinyl n-butyral) resin. Refractive index wasmeasured according to ASTM D542 at a wavelength of 589 nm and 25° C. Therefractive index of a poly(vinyl acetal) resin comprising residues of analdehyde other than n-butyraldehyde can be at least about 0.001, atleast about 0.002, at least about 0.003, at least about 0.004, at leastabout 0.005 and/or not more than about 0.010, not more than about 0.007,or not more than about 0.006 higher or lower than the refractive indexof a comparable poly(vinyl butyral) resin, or the difference can be inthe range of from about 0.001 to about 0.010, about 0.002 to about0.007, or about 0.003 to about 0.006. In some embodiments, therefractive index of the poly(vinyl acetal) resin comprising residues ofan aldehyde other than n-butyraldehyde can be at least about 1.480, atleast about 1.481, at least about 1.482, at least about 1.483, or atleast about 1.484. In some embodiments, the refractive index of thepoly(vinyl acetal) resin including residues of an aldehyde other thann-butyraldehyde can be not more than about 1.490, not more than about1.489, not more than about 1.488, not more than about 1.487, not morethan about 1.486, not more than about 1.485, not more than about 1.484,not more than about 1.483, not more than about 1.482, not more thanabout 1.481, or not more than about 1.480. The refractive index of thepoly(vinyl acetal) resin comprising residues of an aldehyde other thann-butyraldehyde can be in the range of from about 1.480 to about 1.490,about 1.482 to about 1.489, or about 1.483 to about 1.488.

As discussed previously, poly(vinyl acetal) resins comprising residuesof an aldehyde other than n-butyraldehyde may, in some embodiments, bephysically mixed with a poly(vinyl n-butyral) resin or may furtherinclude resins of n-butyraldehyde. Such combinations, which include afirst poly(vinyl acetal) resin component and a second poly(vinyl acetal)resin component, may also exhibit unexpected properties, including glasstransition temperature, viscosity, refractive index, and others. As usedherein, the term “poly(vinyl acetal) resin component,” refers either toan individual poly(vinyl acetal) resin present in a blend of resins orto an acetal moiety present on a single poly(vinyl acetal) resin. Insome embodiments of the present invention, a blend of first and secondpoly(vinyl acetal) resin components may not only exhibit propertiesdifferent than each individual component, but may also exhibitproperties unexpected for the combination.

For example, in some embodiments, a resin composition may comprise afirst poly(vinyl acetal) resin component and a second poly(vinyl acetal)resin component. The first poly(vinyl acetal) resin component can have afirst value, A, for a selected resin property, and the second poly(vinylacetal) resin component can have a second value B, for the same selectedresin property. When the poly(vinyl acetal) resin components comprisedifferent acetal moieties on a single resin, the values, A and B, forthe selected resin property correspond to the values for that propertyexhibited by a poly(vinyl acetal) resin including only residues of thataldehyde. For example, if the first poly(vinyl acetal) resin componentincluded residues of i-butyraldehyde, the value, A, for the selectedresin property for the first poly(vinyl acetal) resin component would bethe value of that property for a poly(vinyl acetal) resin including onlyresidues of i-butyraldehyde. The selected resin property can be anymeasurable property of a poly(vinyl acetal) resin. Examples of resinproperties can include, but are not limited to, glass transitiontemperature, tan delta, refractive index, viscosity, melt flow, impactresistance, and others. In some embodiments, the resin property can beselected from the group consisting of glass transition temperature, tandelta, refractive index, and viscosity.

According to some embodiments of the present invention, the resincomposition, which includes the first and second poly(vinyl acetal)resin components, which may be present in the composition in respectiveamounts of Y and Z weight percent, can have an actual value, C, for theselected resin property that is not equal to a value within about 15,within about 10, or within about 5 percent of the calculated value, C′,calculated by equation (1), below.C′=(Y×A)+(Z×B)  (1)

In some embodiments, the actual value, C, of the selected resin propertyfor the resin composition can be closer to the value, A, of the selectedresin property of the first poly(vinyl acetal) resin component such thatthe absolute value of the difference between A and C is less than theabsolute value of the difference between C and B. In other embodiments,the actual value, C, of the selected resin property can be closer to thevalue, B, of the selected resin property of the second poly(vinylacetal) resin component such that the absolute value of the differencebetween B and C is less than the absolute value of the differencebetween C and A.

Additionally, the first and second poly(vinyl acetal) resin componentscan have respective first and second values, R and S, for another resinproperty and the resin composition may have a value, T, for the otherproperty. In some embodiments, the actual composition value, T, may nothave a value that falls within about 15, within about 10, or withinabout 5 percent of the value, T′, calculated by equation (2), below.T′=(Y×R)+(Z×S)  (2)

However, in other embodiments, at least one resin property may have anactual composition value that falls within about 15, within about 10,within about 5, within about 2, or may equal the calculated value, T′,determined by equation (2), above. In some embodiments, the values forR, S, and T may be substantially the same, such that each value iswithin about 15, within about 10, or within about 5 percent of each ofthe others. The first and second poly(vinyl acetal) resin components andthe resin composition may include one or more other properties that fallwithin one of the ranges described previously. The first poly(vinylacetal) resin component, second poly(vinyl acetal) resin component,and/or resin composition may have values for other resin properties,including glass transition temperature and viscosity, that fall withinone or more of the ranges provided previously.

When a resin layer or interlayer includes at least one poly(vinylacetal) resin including residues of an aldehyde other thann-butyraldehyde, the layer or interlayer may also exhibit unexpected orenhanced properties, as compared to a comparable resin layer formed froma poly(vinyl n-butyral) resin and a plasticizer of the same type and inthe same amount. As used herein, the term “comparable poly(vinyln-butyral) resin layer,” refers to a resin layer formed using acomparable poly(vinyl n-butyral) resin, as defined previously, and aplasticizer of the same type and in the same amount as a given layer.

A resin layer that includes at least one poly(vinyl acetal) resin havingresidues of an aldehyde other than n-butyraldehyde can have a differentglass transition temperature than a comparable poly(vinyl n-butyral)resin layer. For example, in various embodiments, the glass transitiontemperature of a resin layer including a poly(vinyl acetal) resin havingresidues of an aldehyde other than n-butyraldehyde can be at least about0.25, at least about 0.50, at least about 1, at least about 1.5, atleast about 2, at least about 3, at least about 4, or at least about 5°C. higher or lower than the glass transition temperature of a comparablepoly(vinyl n-butyral) resin layer. In some embodiments, the glasstransition temperature of the resin layer that comprises a poly(vinylacetal) resin having residues of an aldehyde other than n-butyraldehydecan be at least about 25, at least about 30, at least about 35, or atleast about 37° C., while, in some embodiments, it may be less thanabout 25, not more than about 20, not more than about 15, not more thanabout 10, not more than about 5, not more than about 2, not more thanabout 1, not more than about 0, not more than about −1, not more thanabout −2° C., measured as described previously.

According to some embodiments of the present invention, the resin layermay have a high glass transition temperature, such as, for example aglass transition temperature of greater than about 46° C. Such a resinlayer, which may also be used as a single-layer interlayer or may becombined with one or more other layers to form a dual-layer interlayeror a multilayer interlayer comprising three or more layers, may be usedin applications requiring high levels of impact resistance or strength.In various embodiments, such an interlayer may be formed by combining atleast one poly(vinyl acetal) resin comprising at least 10 weight percentof residues of an aldehyde other than n-butyraldehyde and a plasticizer.The plasticizer may be present in the composition in an amount toprovide the resin layer with a glass transition temperature greater than46° C. such as, for example, an amount of at least about 1, at leastabout 2, at least about 5 phr and/or not more than about 30, not morethan about 25, not more than about 20 phr, not more than about 15 phr,or not more than about 10 phr, or an amount in the range of from about 1to about 30, about 2 to about 25, about 5 to about 15, about 5 to about30, or about 5 to about 20 phr. The glass transition temperature of thelayer or interlayer can be at least about 30, at least about 37, atleast about 40, at least about 46, at least about 48, at least about 50,at least about 52, at least about 54, at least about 55, at least about60, at least about 65, or at least about 70° C.

In some embodiments, such layers and interlayers may be utilized in amultiple layer panel with at least one rigid substrate, examples ofwhich are provided below. The rigid substrate may be any transparent,rigid substrate. In some embodiments, the rigid substrate may be a glasssubstrate, such as, for example, a glass substrate may be selected fromthe group consisting of flat glass, float glass, warped glass, wavyglass, tempered glass, heat-strengthened glass, bent glass, chemicallytempered glass, and combinations thereof. In some embodiments, the glasssubstrate may be selected from the group consisting of warped glass,wavy glass, tempered glass, heat-strengthened glass, bent glass, andcombinations thereof. Additional embodiments of multiple layer panels,including one or more different types of rigid substrates will bediscussed in detail shortly.

Resin layers that include at least one poly(vinyl acetal) resinincluding residues of an aldehyde other than n-butyraldehyde can alsoexhibit enhanced optical properties such as, for example, refractiveindex. In some embodiments, the refractive index of a resin layerincluding at least one poly(vinyl acetal) resin including residues of analdehyde other than n-butyraldehyde can be at least about 0.001, atleast about 0.002, at least about 0.003, at least about 0.004, at leastabout 0.005 and/or not more than about 0.010, not more than about 0.007,or not more than about 0.006 higher or lower than the refractive indexof a comparable poly(vinyl n-butyral) resin layer. The differencebetween the refractive index of a resin layer including at least onepoly(vinyl acetal) resin including residues of an aldehyde other thann-butyraldehyde and the refractive index of a comparable poly(vinyln-butyral) resin layer can be in the range of from 0.001 to about 0.010,about 0.002 to about 0.007, or about 0.003 to about 0.006.

In some embodiments, the refractive index of the resin layer thatincludes at least one poly(vinyl acetal) resin having residues of analdehyde other than n-butyraldehyde can be at least about 1.470, atleast about 1.471, at least about 1.472, at least about 1.473, at leastabout 1.474, at least about 1.475, at least about 1.476, at least about1.477, at least about 1.480 and/or not more than about 1.490, not morethan about 1.489, not more than about 1.488, not more than about 1.487,not more than about 1.486, not more than about 1.485, not more thanabout 1.484, not more than about 1.483, not more than about 1.482, notmore than about 1.481, not more than about 1.480, or not more than about1.479, or not more than about 1.478, measured as described previously.The refractive index of the resin layer having residues of an aldehydeother than n-butyraldehyde can be in the range of from about 1.470 toabout 1.490, about 1.572 to about 1.488, about 1.475 to about 1.486,about 1.477 to about 1.485, about 1.480 to about 1.484.

In some embodiments, the resin layer including at least one poly(vinylacetal) resin having residues of an aldehyde other than n-butyraldehydemay also exhibit enhanced acoustic properties, such as, for example, animproved tan delta as compared to a comparable poly(vinyl n-butyral)resin layer. Tan delta is the ratio of the loss modulus (G″) in Pascalsto the storage modulus (G′) in Pascals of a specimen measured by DynamicMechanical Thermal Analysis (DMTA). The DTMA is performed with anoscillation frequency of 1 Hz under shear mode and a temperature sweeprate of 3° C./min. The peak value of the G″/G′ curve at the glasstransition temperature is the tan delta value. Higher tan delta valuesare indicative of higher damping, which can translate to better sounddampening, or acoustic, performance.

In some embodiments, the tan delta of the resin layer including at leastone poly(vinyl acetal) resin having residues of an aldehyde other thann-butyraldehyde can be at least about 1, at least about 2, at leastabout 3, at least about 4, at least about 5, at least about 10, at leastabout 15, or at least about 20 percent higher than the tan delta of acomparable poly(vinyl n-butyral) resin. The tan delta of the resin layercomprising the poly(vinyl acetal) resin including residues of analdehyde other than n-butyraldehyde can be at least about 0.70, at leastabout 1.0, at least about 1.05, at least about 1.10, at least about1.15, at least about 1.20, at least about 1.25, at least about 1.30, atleast about 1.35, or at least about 1.40, measured as describedpreviously.

Additionally, when the resin layer or interlayer includes at least afirst poly(vinyl acetal) resin component and a second poly(vinyl acetal)resin component along with at least one plasticizer, one or moreproperties of the layer or interlayer can be different than expected.For example, the resin layer, which may include x phr of a plasticizeralong with Y weight percent of a first poly(vinyl acetal) resincomponent and Z weight percent of a second poly(vinyl acetal) resincomponent, may also have an actual value, D, for at least one resinlayer property that is not equal to the calculated value, D′, determinedby equation (3) below. In equation (3), E is the value of the selectedlayer property for a resin layer formed from a resin including only thefirst poly(vinyl acetal) resin component and x phr of the plasticizerand F is the value of the selected resin layer property for a resinlayer formed from a resin including only the second poly(vinyl acetal)resin component and x phr of the plasticizer.D′=(Y×E)+(Z×F)  (3)

Examples of resin layer properties can include, but are not limited to,glass transition temperature, refractive index, and tan delta. Valuesfor these properties may fall within the ranges provided above.Additionally, the amount of plasticizer present in the resin compositioncan fall within any of the ranges above. The resin layer may also haveat least one other actual resin layer value that is not equal to a valuewithin about 15, within about 10, or within about 5 percent of thecalculated value, D′, determined by equation (3) above and/or may haveat least one other actual resin layer value that falls within about 15,within about 10, within about 5, within about 2, or is equal to thecalculated value D′ determined by equation (3) above. In variousembodiments, E and F may both have a value within about 15, within about10, or within about 5 percent of the actual resin layer value D.

According to various embodiments of the present invention, a method ofmaking a polymer interlayer is provided that comprises selecting andblending at least a first poly(vinyl acetal) resin or precursor thereto,and a second poly(vinyl acetal) resin or precursor thereto, in order toprovide a blended resin composition, layer, or interlayer havingdesirable final properties. The method can include the step ofidentifying at least one resin layer property, including, for example,one or more properties selected from the group consisting of glasstransition temperature, refractive index, viscosity, tan delta, impactresistance, melt flow, and combinations thereof. The target value forone or more resin layer properties can fall within at least one of theranges provided previously.

The method may also include the step of selecting and blending at leasta first poly(vinyl acetal) resin component and a second poly(vinylacetal) resin component to provide a blended resin composition. The typeand amount of the first and second poly(vinyl acetal) resin, orprecursors thereto, can be any of those described herein and, in someembodiments, may be any of those described herein. When the blendingincludes blending first and second poly(vinyl acetal) resin resins, theblending can comprise a melt blending step and may be performed at atemperature of at least about 150, at least about 200, at least about250° C. In other embodiments, when the blending includes blendingpoly(vinyl acetal) resin precursors, the blending step may includemixing a first and a second aldehyde and using the mixed aldehyde toform a blended resin. In some embodiments, the aldehydes can be mixedprior to forming the resin, such that a mixed aldehyde is reacted withthe poly(vinyl alcohol). In other embodiments, at least a portion of theblending of the aldehydes may take place during acetalization. Afteracetalization, the formation of the blended resin may be carried out asdescribed previously. Thereafter, at least one resin layer may be formedusing the blended resin, optionally combined with one or moreplasticizers of types and in amounts as discussed previously.

In various embodiments, the types and/or amounts of the first and secondpoly(vinyl acetal) resin components, or precursors thereto, may beselected in order to achieve a value for the selected resin layerproperty that is within about 20, within about 10, within about 5, orwithin about 2 percent of the target value identified previously. Insome embodiments, the blending may be performed to produce a blendedresin with a lower glass transition temperature than a comparablepoly(vinyl n-butyral) resin so that less plasticizer is required toachieve a given glass transition temperature or certain acousticproperty for the final layer. In some embodiments, the blending may beperformed to produce a blended resin having a higher or lower refractiveindex than a comparable poly(vinyl n-butyral) resin in order to minimizedilution by a lower refractive index additive or to minimize thedifference between the refractive indices of two resin layers. Otherapplications or uses for blending the poly(vinyl acetal) resins, orprecursors thereto, are also possible and may be utilized according tovarious embodiments of the present invention.

The resulting blended resins can then be formed into one or more resinlayers according to any suitable method. Exemplary methods of formingpolymer layers and interlayers can include, but are not limited to,solution casting, compression molding, injection molding, meltextrusion, melt blowing, and combinations thereof. Multilayerinterlayers including two or more resin layers may also be producedaccording to any suitable method such as, for example, co-extrusion,blown film, melt blowing, dip coating, solution coating, blade, paddle,air-knife, printing, powder coating, spray coating, and combinationsthereof. In various embodiments of the present invention, the layers orinterlayers may be formed by extrusion or co-extrusion. In an extrusionprocess, one or more thermoplastic polymers, plasticizers, and,optionally, at least one additive, can be pre-mixed and fed into anextrusion device. Other additives, such as ACAs, colorants, and UVinhibitors, which can be in liquid, powder, or pellet form, may also beused and may be mixed into the thermoplastic polymers or plasticizersprior to entering the extrusion device. These additives can beincorporated into the polymer resin and, by extension, the resultantpolymer sheet, thereby enhancing certain properties of the polymer layeror interlayer and its performance in the final multiple layer glasspanel or other end product.

In various embodiments, the thickness, or gauge, of the layers orinterlayers can be at least about 10, at least about 15, at least about20 mils and/or not more than about 100, not more than about 90, not morethan about 60, not more than about 50, or not more than about 35 mils,or it can be in the range of from about 10 to about 100, about 15 toabout 60, or about 20 to about 35 mils. In millimeters, the thickness ofthe polymer layers or interlayers can be at least about 0.25, at leastabout 0.38, at least about 0.51 mm and/or not more than about 2.54, notmore than about 2.29, not more than about 1.52, or not more than about0.89 mm, or in the range of from about 0.25 to about 2.54 mm, about 0.38to about 1.52 mm, or about 0.51 to about 0.89 mm.

In some embodiments, the resin layers or interlayers can comprise flatpolymer layers having substantially the same thickness along the length,or longest dimension, and/or width, or second longest dimension, of thesheet, while, in other embodiments, one or more layers of a multilayerinterlayer, for example, can be wedge-shaped or can have a wedge-shapedprofile, such that the thickness of the interlayer changes along thelength and/or width of the sheet, such that one edge of the layer orinterlayer has a thickness greater than the other. When the interlayeris a multilayer interlayer, at least one, at least two, or at leastthree of the layers of the interlayer can be wedge-shaped. When theinterlayer is a monolithic interlayer, the polymer sheet can be flat orwedge shaped. Wedge-shaped interlayers may be useful in, for example,heads-up-display (HUD) panels in automotive and aircraft applications.

According to some embodiments wherein the resin compositions and layersdescribed previously are used to form interlayers, the interlayers mayalso exhibit one or more improved or enhanced properties. Theinterlayers can comprise single, or monolithic, interlayers, ordual-layer interlayers having a pair of adjacent resin layers. In someembodiments, the interlayers can include three or more resin layers withat least a first, second, and third resin layer, with the second resinlayer sandwiched between the first and third. When the interlayerincludes two or more resin layers, adjacent resin layers can comprisedifferent poly(vinyl acetal) resins, and can have one or more propertiesthat differ from each other. In some embodiments, the poly(vinyl acetal)resins present in adjacent layers may have different residual hydroxyland/or acetal contents that differ from each other by an amount withinthe ranges provided above.

In some embodiments, adjacent resin layers may have different glasstransition temperatures, such as, for example, glass transitiontemperatures that differ from one another by at least about 3, at leastabout 5, at least about 8, at least about 10, at least about 12, atleast about 15, at least about 18, at least about 20, at least about 22,or at least about 25° C. In the same embodiments, however, thedifference between the refractive index of the adjacent layers may beminimized by, for example, utilizing at least one poly(vinyl acetal)resin comprising residues of an aldehyde other than n-butyraldehyde. Forexample, in some embodiments, the absolute value of the differencebetween refractive indices between adjacent resin layers, of which atleast one includes a poly(vinyl acetal) resin comprising residues of analdehyde other than n-butyraldehyde, can be not more than about 0.010.In some embodiments, the absolute value of the difference in therefractive indices between such layers can be not more than about 0.009,not more than about 0.008, not more than about 0.007, not more thanabout 0.006, not more than about 0.005, not more than about 0.004, notmore than about 0.003, or not more than about 0.002.

As a result, interlayers according to various embodiments of the presentinvention exhibit optimized or enhanced optical properties. Clarity isone parameter used to describe the optical performance of compositions,layers, and interlayers described herein and may be determined bymeasuring haze value or percent. Haze value represents thequantification of light scattered by a sample in contrast to theincident light. In some embodiments, the resin blends, layers, andinterlayers described herein may have a haze value of less than 5percent, less than about 4 percent, less than about 3 percent, less thanabout 2 percent, less than about 1, or less than about 0.5 percent, asmeasured in accordance with ASTM D1003-61 (reapproved 1977)—Procedure Ausing Illuminant C, at an observer angle of 2 degrees. The test isperformed with a hazemeter, such as a Model D25 Hazemeter commerciallyavailable from Hunter Associates (Reston, Va.), on a polymer samplewhich has been laminated between two sheets of clear glass, each havinga thickness of 2.3 mm (commercially available from Pittsburgh GlassWorks of Pennsylvania).

Another parameter used to determine the optical performance istransparency, or percent visual transmittance (% T_(vis)), which ismeasured using a hazemeter, such as a Model D25 Hazemeter commerciallyavailable from Hunter Associates (Reston, Va.), in an IIlluminant D65 atan observer angle of 10°. The values provided herein were obtained byanalyzing a polymer sample which had been laminated between two sheetsof clear glass, each having a thickness of 2.3 mm (commerciallyavailable from Pittsburgh Glass Works of Pennsylvania). In someembodiments, the resin compositions, layers, and interlayers of thepresent invention can have a percent visual transmittance of at leastabout 80, at least about 81, at least about 82, at least about 83, atleast about 84, at least about 85, at least about 85.5, at least about86, at least about 86.5, at least about 87, at least about 87.5, atleast about 88, or at least about 88.5 percent.

In addition to exhibiting one or more optical properties within theranges above, the resin layers and interlayers described herein may alsoexhibit acoustic properties within a desirable range. For example, insome embodiments, the resin layers and interlayers can have a dampingloss factor, or loss factor, of at least about 0.10, at least about0.15, at least about 0.17, at least about 0.20, at least about 0.25, atleast about 0.27, at least about 0.30, at least about 0.33, or at leastabout 0.35. Loss factor is measured by Mechanical Impedance Measurementas described in ISO Standard 16940. Polymer samples are laminatedbetween two sheets of clear glass, each having a thickness of 2.3 mm,and are prepared to have a width of 25 mm and a length of 300 mm. Thelaminated samples are then excited at the center point using a vibrationshaker, commercially available from Brüel and Kjær (Nærum, Netherlands)and an impedance head is used to measure the force required to excitethe bar to vibrate and the velocity of the vibration. The resultanttransfer function is recorded on a National Instrument data acquisitionand analysis system and the loss factor at the first vibration mode iscalculated using the half power method.

The resin compositions, layers, and interlayers according to embodimentsof the present invention may be utilized in a multiple layer panel thatcomprises a resin layer or interlayer and at least one rigid substrate.Any suitable rigid substrate may be used and in some embodiments may beselected from the group consisting of glass, polycarbonate, biaxiallyoriented PET, copolyesters, acrylic, and combinations thereof. When therigid substrate includes glass, the glass can be selected from the grouplisted previously. When the rigid substrate includes a polymericmaterial, the polymeric material may or may not include a hard coatsurface layer. In some embodiments, the multilayer panels include a pairof rigid substrates with the resin interlayer disposed therebetween. Thepanels can be used for a variety of end use applications, including, forexample, for automotive windshields and windows, aircraft windshieldsand windows, panels for various transportation applications such asmarine applications, rail applications, etc., structural architecturalpanels such as windows, doors, stairs, walkways, balusters, decorativearchitectural panels, weather-resistant panels, such as hurricane glassor tornado glass, ballistic panels, and other similar applications.

When laminating the resin layers or interlayers between two rigidsubstrates, such as glass, the process can include at least thefollowing steps: (1) assembly of the two substrates and the interlayer;(2) heating the assembly via an IR radiant or convective device for afirst, short period of time; (3) passing the assembly into a pressurenip roll for the first de-airing; (4) heating the assembly for a shortperiod of time to about 60° C. to about 120° C. to give the assemblyenough temporary adhesion to seal the edge of the interlayer; (5)passing the assembly into a second pressure nip roll to further seal theedge of the interlayer and allow further handling; and (6) autoclavingthe assembly at temperature between 135° C. and 150° C. and pressuresbetween 150 psig and 200 psig for about 30 to 90 minutes. Other methodsfor de-airing the interlayer-glass interface, as described according tosome embodiments in steps (2) through (5) above include vacuum bag andvacuum ring processes, and both may also be used to form interlayers ofthe present invention as described herein.

In some embodiments, the multiple layer panel may include at least onepolymer film disposed on the layer or interlayer, forming a multiplelayer panel referred to as a “bilayer.” In some embodiments, theinterlayer utilized in a bilayer may include a multilayer interlayer,while, in other embodiments, a monolithic interlayer may be used. Theuse of a polymer film in multiple layer panels as described herein mayenhance the optical character of the final panel, while also providingother performance improvements, such as infrared absorption. Polymerfilms differ from polymer layers or interlayers in that the films alonedo not provide the necessary penetration resistance and glass retentionproperties. The polymer film can also be thinner than the sheet, and mayhave a thickness in the range of from 0.001 to 0.25 mm. Poly(ethyleneterephthalate) (“PET”) is one example of a material used to form thepolymer film.

The following examples are intended to be illustrative of the presentinvention in order to teach one of ordinary skill in the art to make anduse the invention and are not intended to limit the scope of theinvention in any way.

Examples

The following Examples describe the preparation of several resincompositions, layers, and interlayers that include various poly(vinylacetal) reins. As described below, several tests performed on many ofthe compositions, layers, and interlayers were used to evaluate theseveral properties of both comparative and inventive materials.

Example 1: Preparation of Poly(Vinyl Acetal) Resins

Several poly(vinyl acetal) resins were prepared by acetalizingpoly(vinyl alcohol) with several different aldehydes having acetal chainlengths from 4 to 8 carbon atoms. Each resin was prepared by firstdispersing poly(vinyl alcohol) powder in water in a 5-L glass reactor atambient temperature. The resulting slurry was then heated to atemperature greater than 90° C. to dissolve the poly(vinyl alcohol) andthe resulting solution was then cooled to ambient temperature. Uponaddition of an aldehyde and an acid catalyst, poly(vinyl acetal) polymerprecipitated within a few minutes. The resulting mixture was held forseveral hours in order to achieve the target conversion of thepoly(vinyl alcohol) and, if necessary, the reaction mixture was heatedto speed the conversion. Several aldehydes were used to form the variousresins, including n-butyraldehyde (nBuCHO), i-butyraldehyde (iBuCHO),2-methylbutyraldehyde (2MeBuCHO), 2-methylvaleraldehyde (2MeValCHO); and2-ethylhexanaldehyde (2EHCHO).

Poly(vinyl acetal) solids precipitated from solution and weresubsequently separated from the reaction fluid via filtration. Therecovered solids were then washed multiple times with water andpotassium hydroxide to remove impurities and neutralize the acidcatalyst. The washed poly(vinyl acetal) was then dried using a lab-scalefluidized drier. Sheet samples of the resin were formed using a standardcompression molding technique with a steam heated press. The percentresidual hydroxyl content, glass transition temperature (T_(g)), andrefractive index of the samples were measured and the results areprovided in Table 1, below.

TABLE 1 Properties of Several Poly(vinyl acetal) Resins PVOH RefractiveResin Aldehyde (wt %) Index (nD25) Tg (° C.) R-1 n-butyraldehyde 18.71.487 78.8 R-2 n-butyraldehyde 10.5 1.486 76.3 R-3 n-butyraldehyde 9.11.483 nd R-4 i-butyraldehyde 18.7 1.480 88.6 R-5 i-butyraldehyde 16.71.478 88.0 R-6 2-methylbutyraldehyde 26.7 1.488 81.1 R-72-methylbutyraldehyde 19.2 1.486 76.7 R-8 2-methylvaleraldehyde 22.31.487 65.2 R-9 2-ethylhexanaldehyde 17.3 1.486 50.7 nd = not determined

Additionally, FIG. 1 provides a graphical representation of the tandelta of several of the resins listed in Table 1 as a function oftemperature.

As shown in Table 1, above, poly(vinyl acetal) resins can be producedthat have similar refractive indices and residual hydroxyl contents, butdifferent glass transition temperatures. Additionally, as shown in Table1, poly(vinyl acetal) resins having similar refractive indices may havesignificantly different glass transition temperatures, such as, forexample, resins R-7 (RI=1.486; T_(g)=76.7° C.) and R-9 (RI=1.485;T_(g)=50.7° C.), or R-1 (RI=1.487; T_(g)=78.8° C.) and R-9 (RI=1.485;T_(g)=50.7° C.). This may permit the use of lower amounts of plasticizerwhen, for example, such resins are used in acoustic multilayerinterlayers, while minimizing the difference in refractive indicesbetween different resin layers. As a result, interlayers formulated withtwo or more of the above resins may exhibit enhanced optical andacoustic properties, as shown in the following Examples.

Example 2: Preparation of Mixed Poly(Vinyl Acetal) Resins

Several mixed poly(vinyl acetal) resins were prepared in a similarmanner as described in Example 1 above, except the aldehyde added to thepoly(vinyl alcohol) slurry included a mixture of two differentaldehydes. The residual hydroxyl content of the resulting mixedpoly(vinyl acetal) resins was determined using both NMR and thetitration methods described above. All resins had a residual acetatecontent of 2 weight percent. The glass transition temperature and tandelta of sheets of each resin were also measured. The results aresummarized in Table 2, below.

TABLE 2 Properties of Several Mixed Poly(vinyl acetal) Resins ResidualResidual Residual Residual Residual nBuCHO 2EHCHO 2MeBuCHO 2MeValCHO OHT_(g) Resin (wt %) (wt %) (wt %) (wt %) (wt %) (° C.) Tan Delta R-10 4230 — — 26 76.5 1.5 R-11 16 49 — — 33 76.2 0.8 R-12 57 17 — — 24 82.1 1.7R-13 49 24 — — 25 78.7 1.6 R-14 40 41 — — 17 72.5 1.8 R-15 40 42 — — 1670.7 1.8 R-16 55 28 — — 15 74.3 2.1 R-17 52 28 — — 18 77.7 1.9 R-18 3851 — — 9 49.0 1.8 R-19 75 11 — — 12 68.2 2.3 R-20 75 16 — — 7 60.4 1.2R-21 73 17 — — 8 55.0 2.0 R-22 75 13 — — 10 66.0 2.2 R-23 — 81 — — 1750.7 1.8 R-24 — — 71 — 27 81.1 1.8 R-25 — — 78 — 20 76.7 2.5 R-26 — — —75 23 65.2 1.9 nd = not determined

Example 3: Refractive Index Matching of Poly(Vinyl Acetal) Resins

Several of the resins prepared in Example 1 above were melt blended withvarious amounts of the plasticizer triethylene glycolbis(2-ethylhexanoate) (“3GEH”) or tetraethylene glycoldi-(2-ethylhexanoate) (“4GEH”). The plasticized resins were then formedinto sheets and the glass transition temperature and refractive index ofeach sheet was measured. The results for resins plasticized with 3GEHand 4GEH are provided below in Tables 3a and 3b, respectively.

TABLE 3a Properties of Poly(vinyl acetal) Resin Layers including 3GEHPlasticizer Residual 3GEH Plasticizer Content Hydroxyl 20 phr 38 phr 50phr 70 phr 75 phr Content T_(g) T_(g) T_(g) T_(g) T_(g) Resin (wt %) (°C.) RI (° C.) RI (° C.) RI (° C.) RI (° C.) RI R-1 18.7 nd nd 32.0 1.476nd nd nd nd nd nd R-2 10.5 nd nd 21.1 1.475 9.14 1.472 nd nd 0 1.466 R-39.1 51 1.480 nd nd nd nd 0 1.468 nd nd R-4 18.7 nd nd 33.8 1.474 nd ndnd nd nd nd R-5 16.7 52 1.481 31.0 1.474 18    1.471 nd nd nd nd R-917.3 nd nd 13.4 1.472 6.7  1.470 nd nd nd nd nd = not determined

TABLE 3b Properties of Poly(vinyl acetal) Resin Layers including 4GEHPlasticizer Re- sidual Hy- 4GEH Plasticizer Content droxyl 35 phr 38 phr50 phr 70 phr Content T_(g) T_(g) T_(g) T_(g) Resin (wt %) (° C.) RI (°C.) RI (° C.) RI (° C.) RI R-1 18.7 31 1.478 nd nd nd nd nd nd R-2 10.5nd nd nd nd nd nd 0 1.471 R-5 16.7 nd nd 31.0 1.475 nd nd nd nd R-9 17.3nd nd nd nd 3 1.473 nd nd nd = not determined

Additionally, graphical representations of the tan delta as a functionof temperature for several of the plasticized resins listed in Table 3aare provided in FIG. 2.

When formulating a multilayer interlayer, it is often desirable toinclude one or more higher glass transition temperature resins as theouter “skin” layers and lower glass transition temperature resin(s) asan inner “core” layer. Such configurations facilitate handling of theinterlayer, as well as provide it with mechanical and impact strength,while also providing acoustic performance. As shown in Tables 3a and 3b,above, resins with lower residual hydroxyl contents typically includehigher plasticizer contents and exhibit lower glass transitiontemperatures than higher residual hydroxyl content, lower plasticizercontent resin layers.

Table 4, below, lists several combinations of high and low glasstransition temperature resins shown in Table 3a and 3b above suitable asrespective skin and core layers in multilayer interlayers.

TABLE 4 Properties of Poly(vinyl acetal) Resin Combinations ΔT_(g) SkinCore (Skin - ΔRI Interlayer Resin Plasticizer T_(g) RI Resin PlasticizerT_(g) RI Core) (Skin - Core) CI-1 R-1 38 (3GEH) 32 1.476 R-2 70 (3GEH) 01.466 32 0.010 DI-1 R-4 38 (3GEH) 33.8 1.474 R-3 70 (3GEH) 0 1.468 33.80.006 DI-2 R-5 38 (3GEH) 31 1.474 R-3 70 (3GEH) 0 1.468 31 0.006 DI-3R-5 38 (4GEH) 31 1.475 R-2 70 (4GEH) 0 1.471 31 0.004 DI-4 R-1 38 (4GEH)31 1.478 R-9 50 (4GEH) 3 1.473 28 0.005 DI-5 R-5 38 (4GEH) 31 1.475 R-950 (4GEH) 3 1.473 28 0.002

As shown in Table 4, a Comparative Interlayer, CI-1, included a resinlayer having a high glass transition temperature poly(vinyl n-butyral)resin (R-1) adjacent to a resin layer having a low glass transitiontemperature poly(vinyl n-butyral) resin (R-2). The difference betweenthe refractive indices of these two resins was 0.010, which is highenough to cause optical defects, such as reduced clarity or haze and/ormottle, in the final interlayer.

However, the high and low glass transition temperature resins ofDisclosed Interlayers DI-1 through DI-5 had a maximum difference inrefractive index of 0.006 (DI-1 and DI-2), with a difference as low as0.002 (DI-5). Disclosed Interlayers DI-1 through DI-5 had a smallerdifference in refractive index than Comparative Interlayer CI-1, whichtranslated to fewer optical defects in the final laminated product.However, as shown in Table 4, above, Disclosed Interlayers DI-1 throughDI-5 had similar differences in glass transition temperature between theskin and core layers as Comparative Interlayer CI-1, and, as a result,the Disclosed Interlayers retain the strength and acoustic properties ofComparative Interlayer CI-1, while exhibiting improved opticalqualities.

Example 4: Properties of Mixed Poly(Vinyl Acetal) Resins

Two poly(vinyl acetal) resins, R-10 and R-11, were formed as describedin Example 1, above, using n-butyraldehyde and i-butyraldehyde,respectively. The resulting poly(vinyl n-butyral) (PVB) resin (R-10) andpoly(vinyl i-butyral) (PViB) resin (R-11) were then divided into severalportions and melt blended with varying amounts of 3GEH. An additionalpoly(vinyl acetal) resin (R-12) was formed by mixing and melt blending50 weight percent of poly(vinyl n-butyral) resin R-10 and 50 weightpercent of poly(vinyl i-butyral) resin R-11. Mixed resin R-12 was alsodivided into several portions and combined with varying amounts of 3GEH.The refractive index of each plasticized resin sample was measured andthe results, shown as a function of plasticizer content, are depictedgraphically in FIG. 3.

As shown in FIG. 3, poly(vinyl i-butyral) resin R-11 exhibited thelowest refractive index of the three resins tested and, unlike the othertwo resins, it maintained a substantially constant refractive index upto a plasticizer loading of about 20 phr. Additionally, as shown in FIG.3, none of the resins exhibited a strictly linear relationship betweenplasticizer loading and refractive index. For each plasticizer loading,blended resin R-12 had a refractive index between the refractive indicesof its component resins, although the value was not an arithmeticaverage of the two.

Another mixed poly(vinyl acetal) resin (R-13) was formed in a similarmanner as described in Example 1, above, but with a mixed aldehyde thatincluded equal weights of i-butyraldehyde and n-butyraldehyde. Theresulting hybrid resin R-13 had an acetal component that includedmoieties of both i-butyraldehyde and n-butyraldehyde and exhibited asimilar trend in refractive index as a function of plasticizer loadingas the physically blended resin R-12.

Several additional properties, including glass transition temperature,tan delta, and viscosity (in a 7.5 weight percent methanol solution)were also measured for resins R-10, R-11, physically blended resin R-12,and hybrid resin R-13 with varying amounts of 3GEH plasticizer. Theresults are summarized in Table 5 below. Additionally, Table 5 providesthe arithmetic average of the values of each property for neat resinsR-10 and R-11.

TABLE 5 Properties of Poly(vinyl acetal) Resins and Mixed Poly(vinylacetal) Resin Arithmetic Average of Resin R-10 & R-11 R-10 R-11 R-12R-13 Resin Component PVB PViB PVB/PViB PVB/PViB Weight Percent 100 10050/50 50/50 Mix Method — — Blend Hybrid Resin 79 89 75, 89 83.6 84 T_(g)(° C.) Refractive Index (nD25) 1.487 1.48 1.483 1.483 1.484 Tan Delta2.35 2.75 2.02 2.64 2.55 Viscosity (cps) 175 122 137 115 148.5 Resinwith 20 phr 3GEH 46 52 49.5 51 49 T_(g) (° C.) Refractive Index (nD25)1.483 1.481 1.481 1.483 1.482 Tan Delta 1.58 1.75 1.83 1.33 1.67 Resinwith 38 phr 3GEH 30 34 31.2 30.2 32 T_(g) (° C.) Refractive Index (nD25)1.476 1.474 1.477 1.476 1.475 Tan Delta 1.25 1.45 1.21 1.32 1.35

As shown in Table 5, above, the values of several of the measuredproperties obtained for the blended resins R-12 and R-13, fall between,but are not necessarily the average of, the values obtained for neatresins R-10 and R-11, which are the constituents of the blend.Additionally, some properties such as glass transition temperature andrefractive index, vary only slightly between neat resins R-10 and R-11and mixed resins R-12 and R-13, while others, such as viscosity and tandelta, exhibit slightly more significant changes. Such informationfacilitates selection of specific resins or resin blends that providedesired properties or combinations of properties for various interlayerapplications.

Example 5: Properties of Mixed Poly(Vinyl Acetal) Resins

Poly(vinyl n-butyral) (PVB) and poly(vinyl 2-ethylhexanal) (PV2EH)resins were prepared as described previously in Example 1 with twoaldehydes in various ratios. The glass transition temperature of themixed acetal resin, as well as the glass transition temperature of purePVB and PV2EH resins, was determined and the results are summarized inTable 6, below.

TABLE 6 Glass Transition Temperatures of Blends of PVB and PV2EHResidual Hydroxyl PVB PV2EH Ratio of Content Resin (wt %) (wt %)PV2EH:PVB (wt %) T_(g) (° C.) R-14 81.2 0.0 — 18.9 79.8 R-15 86.5 0.0 —13.5 77.7 R-16 75.0 11.0 0.15:1 15.5 63.2 R-17 75.0 13.0 0.17:1 14.661.0 R-18 75.0 16.0 0.21:1 12.4 55.4 R-19 73.0 17.0 0.23:1 12.1 50.0R-20 57.0 17.0 0.30:1 25.0 77.1 R-21 49.0 24.0 0.49:1 26.4 73.7 R-2255.0 28.0 0.51:1 18.1 69.3 R-23 52.0 28.0 0.54:1 19.1 72.7 R-24 42.030.0 0.71:1 27.0 71.5 R-25 40.0 41.0 1.03:1 19.2 67.5 R-26 40.0 42.01.05:1 19.9 65.7 R-27 38.0 51.0 1.34:1 12.9 44.0 R-28 16.0 49.0 3.06:135.0 71.2 R-29 0.0 81.7 — 17.3 50.7

As shown in Table 6, mixed poly(vinyl acetal) resins that have a widerange of glass transition temperatures can be produced with poly(vinyln-butyral) and poly(vinyl 2-ethylhexanal) in various ratios. However, asillustrated by Table 7, below, a mixed acetal with equal parts by weightof PVB and PV2EH also exhibits a constant refractive index over theranges shown in Table 6, above.

TABLE 7 Additional Properties of Blends of PVB and PV2EH Resin R-30 R-31R-32 Component PVB PV2EH PVB/PV2EH Weight Percent 86.5 81.7 40/41 T_(g)of Resin (° C.) 77 51 68 Refractive Index 1.486 1.486 1.486 T_(g) at 38phr 3GEH (° C.) 28.5 18.4 20

Thus, resins such as PVB and PV2EH can be formulated into a mixedpoly(vinyl acetal) resin that exhibits different glass transitiontemperatures over a wide blending range, but that have substantially thesame refractive index.

Example 6: Preparation of High Flow Poly(Vinyl Acetal) Resins

A poly(vinyl n-butyral) resin (R-33) was prepared by acetalizing a 98 to98.8 percent hydrolyzed poly(vinyl alcohol) (PVOH) with n-butyraldehyde(BuCHO) according to the procedure described in Example 1, above. ThePVOH had a viscosity between 28 and 32 cps, measured in 4 percent waterat 20° C. A poly(vinyl i-butyral resin) (R-34) was prepared underexactly the same conditions, but with i-butyraldehyde (iBuCHO). Two moreresins, one poly(vinyl n-butyral) (R-35) and one poly(vinyl i-butyral)(R-36), were also prepared under the same conditions, but with ahydrolyzed poly(vinyl alcohol) (PVOH) having a viscosity between 18.5and 21.5 cps. The viscosity of the resulting resins R-33 through R-36was measured in a 7.5 percent solution of methanol at 20° C. and theresults are summarized in Table 8, below.

TABLE 8 Properties of Poly(vinyl n-butyral) and Poly(vinyl i-Butyral)Resins Resin T_(g) at 38 PVOH Resin Resin phr Acetal Viscosity ViscosityT_(g) 3GEH Resin Moiety (cps) (cps) (° C.) (° C.) R-33 nBuCHO 28-32 17078.8 30 R-34 iBuCHO 28-32 110 88.6 35 R-35 nBuCHO 18.5-21.5 90 nd ndR-36 iBuCHO 18.5-21.5 68 nd nd nd = not determined

As shown in Table 8, above, poly(vinyl i-butyral) resins R-34 and R-36exhibited a lower viscosity than the poly(vinyl n-butyral) resins R-33and R-35 prepared with the same poly(vinyl alcohol) under identicalconditions. Additionally, the poly(vinyl i-butyral) resin (R-34)exhibited a higher glass transition temperature than its comparablepoly(vinyl n-butyral) resin (R-33, even when plasticized with 38 phr of3GEH.

Example 7: Preparation of High Glass Transition Temperature Resins

Several poly(vinyl acetal) resins were formulated according to theprocedure described above in Example 1. Three of the resins wereformulated using i-butyraldehyde (R-38 through R-40) and one was formedwith n-butyraldehyde (R-37). Each of the resins was combined with adifferent amount of 3GEH plasticizer and formed into sheets. The glasstransition temperature of each sheet was determined and the results aresummarized in Table 9, below.

TABLE 9 Glass Transition Temperature of Plasticized Poly(vinyl acetal)Resins Plasticizer Content Resin Acetal Moiety (phr) Tg (° C.) R-37nBuCHO 20 46 R-38 iBuCHO 20 52 R-39 iBuCHO 15 60 R-40 iBuCHO 10 70

As shown in Table 9, above, for the same plasticizer content, thepoly(vinyl i-butyral) resin R-38 achieves a higher glass transitiontemperature than the poly(vinyl n-butyral) resin R-37. Additionally,lower levels of plasticizer in the poly(vinyl i-butyral) resins R-38through R-40 results in increased glass transition temperature, whichprovides these resins with increased impact and penetration resistance.

Example 8: Plasticizer Compatibility of Poly(Vinyl Acetal) Resin Layers

Several poly(vinyl acetal) resins of varying residual hydroxyl contentswere prepared as described in Example 1, above. Some of the resins wereformed with n-butyraldehyde and others were formed with i-butyraldehyde.The cloud point temperature of each resin was measured in triethyleneglycol bis(2-ethylhexanoate) by mixing 0.05 grams of the resin in 1.95grams of plasticizer at room temperature. The mixture was then heated ina silicone oil bath under continuous stirring conditions until the resinwas completely dissolved and the solution was clear. The heating wasstopped and the solution was gradually cooled under constant temperaturemonitoring. The temperature at which the solution began to cloud wasdetermined to be the cloud point temperature of the resin in theplasticizer. The cloud point temperatures as a function of residualhydroxyl content were measured for several of the resins according tothe method described previously and the results are summarizedgraphically in FIG. 4.

As shown in FIG. 4, for a given residual hydroxyl content, a resinformed with i-butyraldehyde had a lower cloud point temperature than aresin formed with n-butyraldehyde. Lower cloud point temperaturesindicate higher plasticizer compatibility and, as shown in FIG. 4, thepoly(vinyl acetal) resins prepared with i-butyraldehyde resin were morecompatible with 3GEH than the poly(vinyl acetal) resins formed withn-butyraldehyde for the same residual hydroxyl content.

Example 9: Damping Properties of Poly(Vinyl Acetal) Resins

Two poly(vinyl i-butyral) acetal resins R-41 and R-42, each havingdifferent residual hydroxyl contents, were prepared according to theprocedure described in Example 1 above. Resin R-41 had a residualhydroxyl content of 10.9 weight percent, and resin R-42 had a residualhydroxyl content of 9.1 weight percent. Another resin R-43 was alsoprepared as described in Example 1, above, but with n-butyraldehyde. Theresulting poly(vinyl n-butyral) resin R-43 had a hydroxyl content of10.5 weight percent. Each resin was separately mixed and melt blendedwith varying amounts of 3GEH or 4GEH plasticizer and the tan delta ofeach plasticized resin was measured over a temperature range of −20 to30° C. The results are summarized graphically in FIG. 5.

As shown in FIG. 5, the poly(vinyl i-butyral) resin R-42 plasticizedwith 75 phr of 3GEH exhibited a tan delta of 1.4 at a temperature of0.5° C., which was nearly 31 percent higher than the tan delta ofpoly(vinyl n-butyral) resin R-43. The tan delta of resin R-42 was alsonearly 18 percent higher than the tan delta of resin R-41, whichincluded the same type and amount of plasticizer, but had a higherresidual hydroxyl content than resin R-42.

Example 10: Tan Delta and Glass Transition Temperature of Poly(VinylAcetal) Resins

Two poly(vinyl acetal) resins R-45 and R-46 were prepared according tothe procedure described in Example 1. Both were prepared under identicalconditions and both had residual hydroxyl contents of approximately 9.1weight percent. However, resin R-45 was a poly(vinyl i-butyral) resin,formed using i-butyraldehyde, and resin R-46 was a poly(vinyln-butyral), formed using n-butyraldehyde. Resin R-46 was mixed and meltblended with 3GEH plasticizer to produce a plasticized resin having aglass transition temperature of 2.23° C.

Several samples of resin R-45 were also mixed and melt blended withvarious amounts of 3GEH, but none exhibited a glass transitiontemperature of 2.23° C. To determine the amount of plasticizer requiredto achieve a glass transition temperature of 2.23° C. for resin R-45,the tan delta, glass transition temperature, and plasticizer content ofeach of the samples of R-45 were compiled into two graphs shown in FIGS.6a and 6b . Using the relationships depicted in FIGS. 6a and 6b , it wascalculated that a plasticizer content of 71 phr would provide aplasticized resin R-45 having a glass transition temperature of 2.23° C.Additionally, it was calculated with the graph shown in FIG. 6b that theresulting plasticized resin would have a tan delta of 1.45. Thus, forthe same glass transition temperature, resins, such as resin R-45, thatinclude residues of aldehydes other than n-butyraldehyde, require higherplasticizer loadings and exhibit higher glass transition temperaturesthan similar resins that only include residues of n-butyraldehyde.

While the invention has been disclosed in conjunction with a descriptionof certain embodiments, including those that are currently believed tobe the preferred embodiments, the detailed description is intended to beillustrative and should not be understood to limit the scope of thepresent disclosure. As would be understood by one of ordinary skill inthe art, embodiments other than those described in detail herein areencompassed by the present invention. Modifications and variations ofthe described embodiments may be made without departing from the spiritand scope of the invention.

It will further be understood that any of the ranges, values, orcharacteristics given for any single component of the present disclosurecan be used interchangeably with any ranges, values or characteristicsgiven for any of the other components of the disclosure, wherecompatible, to form an embodiment having defined values for each of thecomponents, as given herein throughout. For example, an interlayer canbe formed comprising poly(vinyl butyral) having a residual hydroxylcontent in any of the ranges given in addition to comprising aplasticizers in any of the ranges given to form many permutations thatare within the scope of the present disclosure, but that would becumbersome to list. Further, ranges provided for a genus or a category,such as phthalates or benzoates, can also be applied to species withinthe genus or members of the category, such as dioctyl terephthalate,unless otherwise noted.

What is claimed is:
 1. An interlayer comprising: a first resin layercomprising a first poly(vinyl acetal) resin and a first plasticizer; anda second resin layer adjacent to said first resin layer, wherein saidsecond resin layer comprises a second poly(vinyl acetal) resin and asecond plasticizer, wherein said second plasticizer is present in saidsecond resin layer in an amount of at least 70 parts per hundred partsof resin (phr) and wherein the difference between the amount of saidfirst plasticizer in said first resin layer and the amount of saidsecond plasticizer in said second resin layer is more than 15 phr,wherein at least one of said first and said second poly(vinyl acetal)resins comprises at least 5 weight percent of residues of an aldehydeother than n-butyraldehyde, based on the total weight of aldehyderesidues of said first or said second poly(vinyl acetal) resin, andwherein the glass transition temperature of said first resin layer is atleast 3° C. higher than the glass transition temperature of said secondresin layer, and wherein the absolute value of the difference betweenthe refractive index of said first resin layer and the refractive indexof said second resin layer is not more than 0.010; wherein thedifference between the residual hydroxyl content of said firstpoly(vinyl acetal) resin and the residual hydroxyl content of saidsecond poly(vinyl acetal) resin is at least 2 weight percent and whereinsaid interlayer has a haze value of less than 5 percent.
 2. Theinterlayer of claim 1, wherein said at least one of said first and saidsecond poly(vinyl acetal) resins comprises at least 50 weight percent ofresidues of an aldehyde other than n-butyraldehyde based on the totalweight of aldehyde residues of said first poly(vinyl acetal) or saidsecond poly(vinyl acetal) resin.
 3. The interlayer of claim 1, whereinsaid aldehyde other than n-butyraldehyde is a C₃ to C₁₂ aliphaticaldehyde.
 4. The interlayer of claim 1, wherein said interlayer meets atleast one of the criteria (i) and (ii), below— (i) said first poly(vinylacetal) resin has a residual hydroxyl content of at least 16 weightpercent and a refractive index of not more than 1.485; and (ii) saidsecond poly(vinyl acetal) resin has a glass transition temperature ofnot more than 75° C.
 5. The interlayer of claim 1, wherein at least oneof said first and said second plasticizer has a refractive index lessthan 1.460.
 6. The interlayer of claim 1, wherein at least one of saidfirst and said second resin layers comprises two plasticizers.
 7. Theinterlayer of claim 1, wherein said first poly(vinyl acetal) resincomprises at least 5 weight percent of residues of i-butyraldehyde,based on the total weight of aldehyde residues of said first poly(vinylacetal) resin, wherein said first poly(vinyl acetal) resin has aresidual hydroxyl content in the range of from 16 to 20 weight percent,wherein said first plasticizer is present in said first resin layer inan amount of not more than 40 phr, and wherein said second poly(vinylacetal) resin comprises at least 5 weight percent of n-butyraldehyderesidues and has a residual hydroxyl content in the range of from 8 to13 weight percent, wherein the difference in the glass transitiontemperature of said first resin layer and the glass transitiontemperature of said second resin layer is at least about 20° C.
 8. Theinterlayer of claim 1, wherein said first plasticizer is present in saidfirst resin layer in an amount of not more than 40 phr and wherein saidfirst resin layer has a glass transition temperature of at least 30° C.,wherein said second poly(vinyl acetal) resin has a residual hydroxylcontent in the range of from 8 to 13 weight percent, and wherein theglass transition temperature of said second resin layer is not more than10° C.
 9. A multiple layer panel comprising said interlayer of claim 1and at least one rigid substrate.
 10. An interlayer comprising: a firstresin layer comprising a first poly(vinyl acetal) resin and a firstplasticizer; and a second resin layer adjacent to said first resinlayer, wherein said second resin layer comprises a second poly(vinylacetal) resin and a second plasticizer, wherein said second plasticizeris present in said second resin layer in an amount of at least 70 phrand wherein the difference between the amount of said first plasticizerin said first resin layer and the amount of said second plasticizer insaid second resin layer is more than 15 phr, wherein said firstpoly(vinyl acetal) resin comprises at least 5 weight percent of residuesof an aldehyde other than n-butyraldehyde, based on the total weight ofaldehyde residues of said first poly(vinyl acetal) resin, wherein saidfirst poly(vinyl acetal) resin has a residual hydroxyl content in therange of from 16 to 20 weight percent, wherein said first plasticizer ispresent in said first resin layer in an amount of not more than 40 phr,and wherein said second poly(vinyl acetal) resin comprises at least 5weight percent of n-butyraldehyde residues and has a residual hydroxylcontent in the range of from 8 to 13 weight percent, wherein thedifference in the glass transition temperature of said first resin layerand the glass transition temperature of said second resin layer is atleast about 20° C., and wherein the absolute value of the differencebetween the refractive index of said first resin layer and therefractive index of said second resin layer is not more than 0.010;wherein the difference between the residual hydroxyl content of saidfirst poly(vinyl acetal) resin and the residual hydroxyl content of saidsecond poly(vinyl acetal) resin is at least 2 weight percent and whereinsaid interlayer has a haze value of less than 5 percent.
 11. Theinterlayer of claim 10, wherein said first poly(vinyl acetal) resinscomprises at least 50 weight percent of residues of an aldehyde otherthan n-butyraldehyde based on the total weight of aldehyde residues ofsaid first poly(vinyl acetal).
 12. The interlayer of claim 10, whereinsaid aldehyde other than n-butyraldehyde is a C₃ to C₁₂ aliphaticaldehyde.
 13. The interlayer of claim 10, wherein said interlayer meetsat least one of the criteria (i) and (ii), below— (i) said firstpoly(vinyl acetal) resin has a residual hydroxyl content of at least 16weight percent and a refractive index of not more than 1.485; and (ii)said second poly(vinyl acetal) resin has a glass transition temperatureof not more than 75° C.
 14. The interlayer of claim 10, wherein at leastone of said first and said second plasticizer has a refractive indexless than 1.460.
 15. The interlayer of claim 10, wherein at least one ofsaid first and said second resin layers comprises two plasticizers. 16.The interlayer of claim 10, wherein said aldehyde other thann-butyraldehyde is i-butyraldehyde.
 17. The interlayer of claim 10,wherein said first plasticizer is present in said first resin layer inan amount of not more than 40 phr and wherein said first resin layer hasa glass transition temperature of at least 30° C., wherein said secondpoly(vinyl acetal) resin has a residual hydroxyl content in the range offrom 8 to 13 weight percent, and wherein the glass transitiontemperature of said second resin layer is not more than 10° C.
 18. Amultiple layer panel comprising said interlayer of claim 10 and at leastone rigid substrate.
 19. An interlayer comprising: a first resin layercomprising a first poly(vinyl acetal) resin and a first plasticizer; anda second resin layer adjacent to said first resin layer, wherein saidsecond resin layer comprises a second poly(vinyl acetal) resin and asecond plasticizer, wherein said second plasticizer is present in saidsecond resin layer in an amount of at least 70 phr and wherein thedifference between the amount of said first plasticizer in said firstresin layer and the amount of said second plasticizer in said secondresin layer is more than 15 phr, wherein said first poly(vinyl acetal)resin comprises at least 5 weight percent of residues ofi-butyraldehyde, based on the total weight of aldehyde residues of saidfirst poly(vinyl acetal) resin, wherein said first poly(vinyl acetal)resin has a residual hydroxyl content in the range of from 16 to 20weight percent, wherein said first plasticizer is present in said firstresin layer in an amount of not more than 40 phr, and wherein saidsecond poly(vinyl acetal) resin comprises at least 5 weight percent ofn-butyraldehyde residues and has a residual hydroxyl content in therange of from 8 to 13 weight percent, wherein the difference in theglass transition temperature of said first resin layer and the glasstransition temperature of said second resin layer is at least about 20°C., and wherein the absolute value of the difference between therefractive index of said first resin layer and the refractive index ofsaid second resin layer is not more than 0.010; wherein the differencebetween the residual hydroxyl content of said first poly(vinyl acetal)resin and the residual hydroxyl content of said second poly(vinylacetal) resin is at least 2 weight percent and wherein said interlayerhas a haze value of less than 5 percent.
 20. The interlayer of claim 19,wherein said first poly(vinyl acetal) resins comprises at least 50weight percent of i-butyraldehyde based on the total weight of aldehyderesidues of said first poly(vinyl acetal).